This application claims priority under 35 U.S.C. § 119(a) on Patent Application No. 2005-176567 filed in Japan on Jun. 16, 2005, the entire contents of which are hereby incorporated by reference.
The present invention relates to a multichannel optocoupler having a plurality of photo-couplers including a pair of a light-emitting element and a light-receiving element.
Typically, examples of the main applications of photo-couplers include their use as a “switching power supply” and a “communication interface of a factory automation (hereinafter referred to as “FA”) device”.
In the case of switching power supply circuits, the photo-coupler used as an electrical insulation between the primary and the secondary side is the third largest component next to the transformer and the capacitor, so that its mounting area and height tend to be large.
Because of the advent of high-frequency insulated gate bipolar transistor (hereinafter referred to as “IGBT”) elements and others in recent years, the component size of capacitor and transformer has been continuously reduced, and it is expected that there will be a demand for the size reduction of switching power supply circuits.
Also, in high-speed communication photo-couplers that are used for the communication interface of an FA device, the number of nodes per mounting substrate is large, so that there is a demand for the accommodation for a large number of channels within a limited mounting area.
In addition, in order to stabilize high-speed communication, accuracy in response delay time as well as in PWD (pulse width distortion) must be improved. To achieve this, the mounting process requires highly accurate and reliable relative positioning of the light-emitting element and the light-receiving element, which are insulated and separated in a photo-coupler.
Furthermore, in achieving this, it is desirable that mounting of a highly populated package be as simple and easy as possible.
Known photo-couplers include photo-couplers in which GaAs and Si are integrated on a single chip (for example, see S48-46278A) and photo-couplers in which an insulating portion is formed by photo-lithography method and etching using a GaAlAs substrate (for example, see H6-5906A).
A device with a multichannel version of this photo-coupler has also been contemplated (for example, see H7-312443A). The semiconductor device that is described in the above-mentioned H7-312443A uses an insulating optical waveguide that is based on TiO2, and has a very complicated structure in terms of processing.
In the conventional example that is described in the above-mentioned H7-312443A, a structure for preventing crosstalk between adjacent photo-couplers (channels) is formed through a complicated and troublesome semiconductor process, and this contributes to a steep rise in production cost.
On one hand, the higher the accuracy of the relative positional relationship between the light-emitting element and the light-receiving element, which constitute the photo-coupler, is, the more stable electrical properties are achieved. On the other hand, if crosstalk between adjacent channels can be adequately limited, such high accuracy in the relative positional relationship of the pair of light-emitting element and light-receiving element as described above is not necessary. For this reason, the inventor of the present invention considered the use of such a semiconductor process as described in the above-mentioned conventional example unnecessary, and arrived at the present invention.